Railroad crosstie formed from recycled rubber tires

ABSTRACT

A railroad crosstie comprising a laminated plurality of strips of a flexible polymeric material, preferably plies cut from rubber tire casings. The plies are glued together, preferably under pressure, to form a tie-shaped entity having any desired dimensions, for example, 9 inches wide by 7 inches high by 8.5 feet long. A T-shaped metal reinforcing spine is contained longitudinally within the laminated strips, the spine having both horizontally- and vertically-oriented load-bearing elements. Preferably, the laminated plies and the metal spine are bound together by a plurality of bailing straps. The crosstie further comprises a weather-resistant covering that preferably includes a heat-dispersing element such as ground glass or ceramic.

RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS

The present application claims priority from a pending U.S. Provisional Patent Application Ser. No. 60/530,138, filed Dec. 18, 2003.

TECHNICAL FIELD

The present invention relates to railroad crossties; more particularly, to non-wooden railroad crossties formed of recycled materials; and most particularly, to a railroad cross-tie formed of laminates of vehicle tire strips and including a load-bearing metal T-bar spine.

BACKGROUND OF THE INVENTION

Prior art railroad rail systems typically employ a plurality of spaced-apart wooden crossties (also referred to herein as “ties”) laid in a gravel railbed transversely of the direction of travel of a railroad train. A pair of metal rails is laid across the ties on base plates and secured thereto by spikes driven through the plates and into the ties.

A well known problem with prior art railroad rail systems is that the wooden crossties are vulnerable to breaking and to rot and thus must be replaced at intervals. Although wooden ties have been relatively inexpensive in the past, the cost of ties is continually increasing as trees for making ties, preferably white oak, are becoming increasingly scarce. What is needed in the art is an alternative material for constructing crossties that does not depend upon the harvesting of trees.

A separate but also well known problem is the disposal of used rubber tire casings from road vehicles. Such casings typically are not recapped and thus have accumulated by the millions in virtually all countries of the world. Worn-out casings present a serious fire hazard, and spectacular fires have occurred on occasion. Large amounts of petrochemicals are tied up in used casings, but to date no significant, large-scale secondary use has been commercialized for used casings.

What is needed in the art is a large-scale secondary use for worn-out rubber tire casings.

It is a principal object of the present invention to provide a railroad crosstie formed in part from rubber tire casings and requiring no wood in its construction.

SUMMARY OF THE INVENTION

Briefly described, a railroad crosstie in accordance with the invention comprises a laminated plurality of strips of a flexible polymeric material, preferably strips cut from rubber tire casings. The strips, also referred to herein as “plies” or “treads”, preferably are glued together, preferably under pressure, to form a tie-shaped entity having any desired dimensions, for example, 9 inches wide by 7 inches high by 8.5 feet long. A T-shaped metal reinforcing spine is contained longitudinally within the laminated strips, the spine having both horizontally- and vertically-oriented load-bearing components. Preferably, the laminated plies and the metal spine are bound together by one or more bailing straps. The crosstie preferably includes electrically insulative anchors for receiving rail-attaching spikes or lag screws. The crosstie further comprises a weather-resistant covering that preferably includes a heat-dispersing element such as ground glass or ceramic that can deflect sunlight without causing significant reflection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is an isometric view of a prior art railroad crosstie comprising strips of vehicle tire casings, substantially as disclosed in U.S. Pat. No. 5,996,901;

FIG. 2 is an elevational cross-sectional view of the prior art crosstie shown in FIG. 1, taken along line 2-2 in FIG. 1;

FIG. 3 is an isometric view in partial cutaway of an improved railroad crosstie in accordance with the invention;

FIG. 4 is a transverse cross-sectional view taken along plane 4 in FIG. 3;

FIG. 5 is a transverse cross-sectional view of a second embodiment;

FIG. 6 is a transverse cross-sectional view taken along plane 7 in FIG. 3;

FIG. 7 is a transverse cross-sectional view of a third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The benefits and advantages of a rubber railroad crosstie in accordance with the invention may be better appreciated by first considering a prior art railroad crosstie comprising strips of vehicle tire casings, which crosstie is disclosed in U.S. Pat. No. 5,996,901, the relevant disclosure of which is incorporated herein by reference.

Referring to FIG. 1, a prior art crosstie 10 includes a plurality of elongated, substantially planar, elastomeric strips 12 assembled together in a stack such that the strips 12 are generally aligned with each other. In the preferred embodiment, strips 12 are made of recycled tire casings. Elastomeric strips formed specifically for the present invention, not from recycled tire casings, would also be within the scope of the prior art invention. Additionally, the stack of strips 12 could be replaced by one elastomeric member of a thickness sufficient for the intended use.

An elongated, substantially planar, rigid first plate 14 is positioned on top of and aligned with the stack of strips 12. An elongated, substantially planar, rigid second plate 16 is positioned beneath and aligned with the stack of strips 12. Base plates 22 are adapted to be fastened to crosstie 10 such that base plates 22 are urged against an outer broad surface 14A of first plate 14. Base plates 22 are fastened to crosstie 10 with fasteners 20 which are inserted through the entire crosstie 10 and base plate 22.

Rails 30 are set on and within base plates 22. Hold down members 24, washers 26, and nuts 28 complete the anchoring of base plates 22 to the railroad crosstie 10, and rails 30 to base plates 22.

Referring to FIG. 2, each of a plurality of wedge shaped members 18 has a penetration formed therethrough. Fasteners 20 are inserted through the penetration, the first and second plates 14, 16, and the stack of elastomeric strips 12. The fasteners 20 are thus non-perpendicular to a longitudinal axis of the stack of elastomeric strips 12. Any conventional fasteners 20 may be used, such as rivets or bolts.

Prior art crosstie 10 has several significant shortcomings which are overcome by a railroad crosstie 110 in accordance with the present invention, as described below.

First, crosstie 10 includes no metal load-bearing supporting members oriented vertically to specifically resist flexure of the crosstie in use. First and second horizontal plates 14, 16 cannot provide adequate flexural resistance without being made unacceptably thick and heavy.

Second, a tendency for slippage between the strips during use is recognized, but an ungainly and expensive mechanical solution to the problem is proposed in the form of a plurality of diagonal fasteners 20 and a plurality of wedge shaped members 18. Adhesives are not considered.

Third, the recycled tire treads as shown are each single-piece, extending the full length and width of crosstie 10, permitting the use of only large truck size tires having a circumference of at least about 9 feet and a tread width of at least about 9 inches.

Fourth, the base plates 22, hold down members 24, and rails 30 are attached to crosstie 10 via bolts extending upwards from below the crosstie, an unwieldy impractical attachment means when ties are laid for use economically and conventionally by first being buried into the railbed.

Fifth, base plates 22 are laid directly on first plate 14 which thus remains exposed to rain and snow. Unless formed expensively of stainless steel or other non-rusting alloy, plate 14 is vulnerable to rapid corrosion and failure. There is no mention of a need or desirability for providing a weather-resistant coating on crosstie 10.

Sixth, because all modern tire casings contain steel reinforcing belts, prior art crosstie 10 may exhibit an undesirably low electrical impedance which may be lower than the minimum level recommended by the American Railway Engineering and Maintenance-of-Way Association (AREMA).

Thus, what is needed is an improved railroad crosstie formed of a plurality of plies cut from tire casings,

-   -   wherein a T-shaped metal spine provides flexural resistance both         vertically and horizontally;     -   wherein each ply may be longitudinally discontinuous and         extending only half the width of the tie, thus permitting use of         automotive-size tires;     -   wherein the strips are adhesively laminated to prevent slippage         therebetween;     -   wherein base plates and rails may be attached conventionally by         spiking or lag screwing;     -   wherein the crosstie is coated to prevent weathering and failure         of the rubber and metal components therein; and     -   wherein subsequently attached railroad rails are electrically         insulated from steel belts in the tire strips.

Referring to FIGS. 3, 4, and 5 through 6, a first embodiment 110 of a railroad crosstie in accordance with the invention is an inflexible rectilinear object having top and bottom surfaces 102, 104 preferably about 9.00 inches wide, sidewalls 106, 108 about 7.00 inches high, and being about 8.50 feet long. Such dimensions are the dimensions for a standard new wooden railroad tie; further, the terms top, bottom, side, upper, lower, vertical, and horizontal as used herein should be understood to refer to those aspects of a tie when positioned for use. As described below, these dimensions may be readily adapted in the invention over a wide range to accommodate specific applications, for example, 12-foot ties for rail switches.

Crosstie 110 includes a load-bearing longitudinal metal spine comprising a vertically-oriented element 114 and a horizontally-oriented element 116. Elements 114, 116 may be provided as separate elements; however, in a currently-preferred embodiment, elements 114, 116 are longitudinally joined in the form of T-bar spine 112.

First and second stacks 118 a, 118 b of plies 120 are disposed on horizontal element 116 on opposite sides of vertical element 114. A “ply” as used herein should be taken to mean any strip of rubber, including virgin, synthetic, or natural rubber; however, in a currently-preferred embodiment, “ply” should be taken to mean a rubber strip taken longitudinally from a tire casing, including a portion of the original outer tread pattern and the non-rubber belting incorporated therein by the tire manufacturer. Stack plies 120 are preferably about 4.25 inches wide and thus may be cut by known means from the tread portion of ordinary rubber tire casings, and especially from used automobile tire casings. To fill the full 8.50-foot length of a standard tie, or longer, plies 120 may be pieced longitudinally. Preferably, the plies are cut to 4.0-foot and 4.5-foot lengths and then are interleaved as shown in FIG. 3, the internal ends of the plies meeting at joints 122. Layer joints 122 should be staggered between adjacent layers of plies.

The number of plies may be varied according to the desired final thickness of the tie and the thickness of each ply. A top ply 124 and a bottom ply 126 are preferably each provided preferably as a single strip cut from a large-diameter wide casing, such as a truck tire casing. Top and bottom plies 124, 126 extend across the full width of horizontal element 116 and stacks 118 a, 118 b.

Preferably, all plies are laminated adhesively under pressure during manufacture of a tie, as described in detail below. Several types of adhesives may be used in accordance with the invention.

In a first example, virgin rubber may be interlaced between the plies to form a tie subassembly which then is autoclaved for a predetermined length of time, for example, 3 minutes per {fraction (1/32)} inch of ply thickness at 260° C.-310° C. at 85 psi-100 psi. The plies require a fluid cleaning prior to assembly and may also require an additional adhesive. The finished tie passes a peal test of 200 psi-300 psi per square inch. This adhesion method is somewhat less desirable because it is relatively slow and requires an autoclave to supply the pressure and heat.

In a second example, in a cold adhesion process, the plies are cleaned and then assembled as above using a chemical cure gum and a chemical cement between the plies. This process requires pressure to flatten and adhere the plies, but no heat. Materials are available from, for example, The Patch Rubber Company, Inc., Roanoke Rapids, N.C., USA, as Chemical Cure Gum 18-317, Chemical Cement 16-452, and Fluid Cleaner 16-472. Such materials are currently quite expensive and the assembly process, conducted manually, is relatively slow and time-consuming.

In a third example, epoxy-based chemical systems may be used to laminate the plies. Currently, such laminating means is less desirable because of cost of materials, the need to combine two chemical parts in forming the adhesive, and a requirement for both heat and pressure to activate the adhesive.

In a fourth and currently-preferred example, an isotonic urethane adhesive is used that is activated by moisture and does not require heat for curing.

All of the above exemplary bonding approaches require pressure to compress the laid-up plies and spine into a monolithic unit during lamination. Such pressure may be provided via a large press in known fashion; however, a drawback is that the bonding times can be on the order of several hours, so a great many expensive presses would be required in a manufacturing facility having a substantial throughput of finished crossties.

As described above, a crosstie in accordance with the invention may be formed of pure rubber strips, which typically are good dielectrics and have a high natural electrical impedance. However, when the crosstie is formed of strips cut from rubber tire casings having steel reinforcing belts, the resulting electrical impedance may be unacceptably low in terms of AREMA standards. This is currently believed to be caused by contact between strands of the chopped steel belts through the various plies, which can result in a low level of electrical continuity in a low percentage of manufactured ties. A rail spike or lag screw attaching a railplate and rail to such a tie can ground the rail to the tie. A solution to this problem is to provide means for electrically isolating all spikes or lag screws from the rubber plies.

Referring to FIGS. 3 and 4, an anchor shield 200 extends through top ply 124 and plies 118 a or 118 b. Anchor shield 200 is analogous to a plasterboard wall screw anchor shield. Anchor shield 200 is formed of a rugged, elastomeric, dielectric polymer, preferably a polyamide such as Kevlar™ or the like, and has walls sufficiently thick so as to not be breached by either the steel belt strands or the spike or lag screw; however, the inner walls 204 of anchor shield 200 must grip and retain the anchor means such as a spike or a lag screw. Anchor shield 200 is disposed in a well 202 formed in tie 110 as by boring at the appropriate location through at least one and preferably a plurality of plies 118 a, 118 b, and preferably is driven and cemented therein in known fashion.

Referring to FIGS. 3 and 6, a means for integrally retaining compression is shown, comprising a bailing strap 138 and lock 140, preferably a conventional steel bailing strap. A tie subassembly is laid up with all plies and adhesives in place and is compressed in a conventional press to a predetermined extent. A plurality of spaced-apart straps 138, preferably four for an 8.5-foot tie, are secured about the compressed subassembly and drawn to a predetermined tension to assure that the correct compression remains when the tie subassembly is removed from the press. Straps 138 and locks 140 remain a part of the crosstie during its working lifetime.

Referring now to FIG. 5, a second embodiment 110′ of crosstie in accordance with the invention is similar to first embodiment 110 except that the T-bar spine 112 is inverted such that horizontal element 116 is disposed immediately below top ply 124. While this embodiment can provide the same functional benefits as embodiment 110, it has a drawback in that rail soleplates cannot be spiked conventionally into the crosstie without providing openings in horizontal element 116 to permit the passage of spikes therethrough. While not an overwhelming drawback, this embodiment requires additional manufacturing steps to provide the openings, plus some indicia on the surface of the tie to indicate the locations of the openings within the tie.

Referring now to FIG. 7, another embodiment 110″ of a crosstie in accordance with the invention is also similar to first embodiment 110 except that the stacks 118 a, 118 b of plies 120 are oriented such that the plies lie vertically on their edges and are parallel to vertical element 114. This embodiment permits the use of still narrower plies, thus broadening the potential range of used casings. Further, compression of plies 120 is easily achieved by providing bores 128′ through plies 120 and vertical element 114 and securing the plies via bolts 150 and nuts 152 seated on large washers 154. Compression and bonding of top and bottom plies 124, 126 during assembly may be readily provided by simple weights without resort to a high-pressure press.

One of the shortcomings of prior art rubber crossties as disclosed in incorporated U.S. Pat. No. 5,996,901 is a lack of a protective covering. Referring again to FIG. 3, an outer covering 160 comprises a thick polymeric layer applied to the entire outer surface of tie 110 as, for example, by dipping or spraying. Covering 160 is conformal with and adherent to the plies, spine, and compression means that comprise the tie subassembly, and preferably is formed of a resilient, durable polymer that is resistant to abrasion and weather extremes. The polymer is desirably loaded with reflective elements such as ground glass or ceramics to diminish the deleterious effect of sunlight over years of use, and further with dyes or pigments in known fashion, and further with UV adsorbing materials, as may be desired. The outer surface of covering 160 may be printed with various manufacturing indicia, including where necessary the locations of shields 200.

An exemplary process for forming a rubber crosstie in accordance with the invention includes the steps of:

-   -   a) obtaining sufficient truck or automobile tire casings to form         two stacks of seven plies 120 each, 8.5 feet long;     -   b) cutting two truck tire casings into top and bottom plies 124,         126, each 9 inches wide by 8.5 feet long; the cutting should be         slightly oversize to allow for post-assembly finishing in         preparation for outer covering 160;     -   c) cutting automobile or truck tire casings into two stacks of         seven plies 120, each ply being 4 feet long by 4.25 inches wide;     -   d) cutting automobile or truck tire casings into two stacks of         seven plies 120, each ply being 4.5 feet long by 4.25 inches         wide;     -   e) grinding or milling each ply 120 to a predetermined uniform         thickness;     -   f) piercing each ply 120 to create bores 128 at the correct         locations;     -   g) providing a T-bar metal spine 112 8.5 feet long, the vertical         element 114 being 0.50 inches thick and horizontal element 116         being 0.25 inches thick;     -   h) chemically cleaning both sides of each ply 120, 124, 126;     -   i) coating the upper surface of bottom ply 126 with adhesive,         and placing the horizontal element 116 of T-bar spine 112 onto         the adhesive;     -   j) applying a layer of adhesive to the upper surface of both         halves of horizontal element 116;     -   k) laying a 4.0-foot and a 4.5-foot ply 120 on the adhesive         layer;     -   l) applying a layer of adhesive on the just-installed plies;     -   m) repeating the application of adhesive layers and installation         of plies 120 until all plies 120 are installed, taking care to         alternate the use of 4.0-foot and 4.5-foot plies in the stack;         preferably, in addition the edges of the plies are adhered to         vertical element 114;     -   n) applying a layer of adhesive to the underside of top ply 124;     -   o) installing top ply 124 onto plies 120;     -   p) externally compressing the subassembly to a predetermined         pressure and temperature for a predetermined length of time to         cure the various adhesive layers;     -   q) removing external compression from the subassembly;     -   r) trimming the exterior surfaces of the subassembly to the         correct height, width, and length;     -   s) boring wells 202 at the appropriate locations through top ply         124 and a distance into plies 118 a, 118 b;     -   t) coating shields 200 with adhesive and inserting shields 200         into wells 202;     -   u) coating the subassembly with a urethane polymer covering to         produce a finished rubber railroad crosstie in accordance with         the invention.

Further steps may include, among others, stamping or imprinting the tie covering, and quality assurance testing the finished tie.

While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims. 

1. A crosstie for use as a railroad rail support, the crosstie having a longitudinal top surface, an opposed longitudinal bottom surface, and opposed longitudinal sidewalls between the top and bottom surfaces, the crosstie comprising: a) a vertical load-bearing element parallel to said sidewalls; b) a horizontal load-bearing element parallel to said top and bottom surfaces; and c) a plurality of plies, each of said plies having flat sides and edges, wherein said plies are stacked on said flat sides, and wherein said flat sides are parallel to said horizontal element.
 2. A crosstie in accordance with claim 1 wherein said vertical element is attached to said longitudinal element, defining a longitudinal metal spine.
 3. A crosstie in accordance with claim 2 wherein said metal spine has a T-shaped cross-sectional appearance.
 4. A crosstie in accordance with claim 1 wherein said stacked plies are divided into first and second stacks, a one of said first and second stacks being disposed on each side of said vertical element.
 5. A crosstie in accordance with claim 4 further comprising a top ply adjacent said plurality of plies and extending across said first and second stacks and said vertical element.
 6. A crosstie in accordance with claim 5 further comprising a bottom ply adjacent said horizontal element.
 7. A crosstie in accordance with claim 4 further comprising a bottom ply adjacent said plurality of plies and extending across said first and second stacks and said vertical element.
 8. A crosstie in accordance with claim 7 further comprising a top ply adjacent said horizontal element.
 9. A crosstie in accordance with claim 1 wherein said top surface is for receiving rail mounting means and said bottom surface is for supporting said crosstie on a railbed.
 10. A crosstie in accordance with claim 1 wherein at least one of said plurality of plies is formed from a vehicle tire casing.
 11. A crosstie in accordance with claim 1 wherein a plurality of said plies is arranged in abutting fashion along the length of said crosstie.
 12. A crosstie in accordance with claim 1 wherein said plies are adhered to each other along their mutual flat surfaces by an adhesive material to form a laminate.
 13. A crosstie in accordance with claim 12 wherein said adhesive material is selected from the group consisting of virgin rubber, cold adhesion chemical cement, epoxides, urethanes, and combinations thereof.
 14. A crosstie in accordance with claim 1 further comprising means for mechanical compression of said plies.
 15. A crosstie in accordance with claim 14 wherein said means for mechanical compression is binder straps.
 16. A crosstie in accordance with claim 1 further comprising a coated outer covering.
 17. A crosstie in accordance with claim 16 wherein said covering includes a heat dispersing material.
 18. A crosstie in accordance with claim 17 wherein said heat dispersing material is selected from the group consisting of recycled glass and ceramic.
 19. A crosstie in accordance with claim 1 further comprising at least one anchor shield disposed in penetrating relationship through at least one of said plies.
 20. A crosstie in accordance with claim 19 wherein said anchor shield is formed of a dielectric material.
 21. A crosstie in accordance with claim 20 wherein said dielectric material is an organic polymer.
 22. A crosstie for use as a railroad rail support, the crosstie having a longitudinal top surface, an opposed longitudinal bottom surface, and opposed longitudinal sidewalls between the top and bottom surfaces, the crosstie comprising: a) a vertical load-bearing element parallel to said sidewalls; b) a horizontal load-bearing element parallel to said top and bottom surfaces; and c) a plurality of plies, each of said plies having flat sides and edges, wherein said plies are stacked on said flat sides, and wherein said flat sides are parallel to said vertical element. 